Chain grate stoker



Dec, 30, 1941. w, LLOYD 2,267,932

cam: GRATE'STOKER Filed May '5, 1939 {Sheets-Sheet 1 11km: [layd Dec. 30-, 1941. w. LLOYD h CHAIN GRATE' STOKER 3 Sheets-Sheet 2 Filed May. 5, 1939 I lg!!! Dec. 30,1941. w, LLOYD 2,267,932

I CHAIN GRATE STOKER 1 Filed May 5, 1939 s sheets-sheet s EA" I 5 44: a :5 E 1 5 E 1 .A EH

INVENTOR' Patented Dec. 30, 1941 CHAIN GRATE STOKER William Lloyd, New York, N. Y., assignor to Combustion Engineering Company, Inc., New York,

Application May 5, 1939, Serial No. 271,859

7 Claims.

The present invention relates to stokers and particularly to improvements in chain grate stokers.

In such stokers the grate is in the form of an endless conveyor made up of grate links arranged in side by side relation with narrow air spaces between the links, the latter being interconnected to form an endless conveying surface. The grate is driven from sprockets at the front of the stoker and extends over idler sprockets at the rear. The windbox located beneath the fuelsupporting portion of the grate is divided by partitions extending transversely of the grate to form a number of air compartments having dampers operable to regulate the supply of air to the related sections of the grate. The fuel-supporting surface of the conveyor-like grate travels above these air compartments and in previous constructions there is a tendency for those portions of the moving grate which lie between the partitions to sag and thus undesirably open up the grate surface. Such opening of the grate surface may also occur as the links hurdle the partitions dividing the air compartments from each other. The result is that fuel may fall into the air compartments.

A feature of the invention resides in an apertured plate forming the top of an air compartment and acting to support the grate links so that there can be no sagging of portions of the grate lying between partitions that divide the air compartments from each other.

A second feature resides in so forming the above-mentioned plates and arranging the air passages therein in such manner as to minimize 5 obscuration of these air passages by grate links travelling thereover in order to obviate closing off of the air supply to areas of the grate.

The invention will be best understood upon consideration of the following detailed description and the appended claims when read in conjunction with the accompanying drawings in which:

Fig. l is a longitudinal sectional view, partly broken away, of a chain grate stoker embodying the invention.

Fig. 2 is a plan view on an enlarged scale showing two of the plates forming the grate supporting surface at the top of the air compartments.

Fig. 3 is a sectional view on the line 33 in Fig.2.

Fig. 4 is a fragmentary view similar to part of Fig. 2 but further enlarged and illustrating the relation of the grate links to the air passages in the grate-supporting plates; and

- nected to each other and to chains of driving links located at points spaced transversely of Fig. 5 is a fragmentary sectional view on the line 5-5 in Fig. 4.

Referring to Fig. 1, driving sprockets I0 at the front of the stoker and idler sprockets II at the rear are provided for'advancing the fuel supporting surface of the grate towards the rear to feed fuel through the furnace. The grate is in'the form of an endless, belt-like conveyor made up of a plurality of rectangular grate links I3 disposed with their longitudinal axes in the direction of grate movement, the links being conthe grate as described hereafter. The grate links are arranged in'end to end and side by side relation with air space ll between the ends of a series of links forming a line longitudinally of the grate; the links of adjacent lines are also,

plate l6 extending between the partitions I4 at opposite ends of a compartment, there being as many plates l6 arranged in side by side relation as the Width of the'stoker requires. As appears in Figs. 1", 3 and 5 the plates 16 also constitute a surface on which the grate links.,fl3 ride so that there can be no undesiredseparation of the links and forming of large openings as a'result of sag-.

ging in the portions lying between partitions or as the grate links pass over the partitions dividing the air compartments from each other because hurdling of the partitions is obviated.

As shown in Fig. 2, each plate I6 is formed with a plurality of narrow air slots 20 which extend at an oblique angle with respect to the length of the plate and the direction of travel of the grate links I3. As a result none of the air slots 20 may be completely obscured by a link, or a line of links, travelling above the latter. The spacing of the slots 20 is such that each link i3 always overlies several slots. Asshown in Figure 2 each plate I6 is formed with groups of slots 20 inclined in one direction with respect to the direction of grate movement, the groups being spaced longitudinally of the grate from adjacent groups of slots inclined in the opposite ditravel. A similar relation exists with respect to groups of slots that are spaced transversely of the grate, this being so in Fig. 2 with respect to groups of slots on adjacent plates in like positions longitudinally of the grate as well as in the case of groups of slots extending toward the middle of each plate from its opposite side edges. In addition to providing for uniformity of air distribution this opposite inclination of adjacent groups of slots prevents creeping of the grate toward either side of the stoker because of friction in traversing the web-like parts of the plates 23.

In the form illustrated a plate l6 may be considered as consisting of imperforate sections at each end interconnected by longitudinally extending ribs 2| at each side edge and in the middle, at 22, which are joined by the web-like portions 23 defining the sides of the air slots 20. Portions 24 of these ribs are offset with respect to the contiguous portions 25 so as to provide a plurality of recesses 26 spaced longitudlnally of the side edges of the plate. The center rib 22 is similarly offset so that neither the outer or inner ends of the slots 20 are all in alinement longitudinally of the grate. Consequently, at some point along both sides of each link l3 air flows through part of at least one slot 20 to reach the space l8 between links.

The recesses 26 along one edge of a plate are staggered with respect to those on the opposite edge so that when two plates are mounted in side by side relation a recess 26 in the edge of one plate lies opposite a portion 24 on the edge of the other plate. The length of a link l3 may be such that the latter overlies several recesses at the edge of a plate as 26A, 2613, Fig. 4. However, air may reach the space I8 at the side of the links through that recess opening 260 in the edge of the adjacent plate which lies opposite the portion 24 separating the two recesses 26A, 263 in the one plate so long as the width of the link portion 30 riding on the plates I6 is not greater than twice the depth of a recess 26. The portions 21 at the ends of the plate, which form the side edges of the imperforate end portions, extend laterally somewhat further than the portions 24 with the result that two adjacent plates contact only at their ends, the intermediate portion of the side edge of one plate being separated from the side edge of the adjacent plate by a narrow space 28. This provides a continuous zig-zag slot between adjacent plates except at the ends, the slot being formed by the alternating recesses 26 in the two plates and the narrow throat produced by spacing the plate edges. The bottom faces 30 of the grate links l3 which contact and ride upon the plates I! are narrower for the greater part of their length than the fuel supporting surfaces 3| and, preferably, of less width than the depth of a recess 26 so that as two parallel lines of links travel along the side edges of the plates they do not completely obscure the air slot between adjacent plates. Although parts of grate links may lie directly above the air openings formed by recesses 26 the space between the base 26a of a recess on one plate and the face of the opposite portion 24 on the adjacent plate is wider than the bottom face 30 of a grate link. Thus, a clear space always remains for air to pass upwardly along the sides of the grate links and through the spaces l8 between adjacent links into the fuel bed.

taining the grate cool.

rection with respect to the direction of grate The arrangement of the slots 20 at an oblique angle to the longitudinal axis of the plates l6 assures uniformity of air distribution through the chain grate travelling thereo-ver. This, together with the zig-zag arrangement of the air passage between the side edges of the plates so that lines of grate links do not obscure the slot results in a continuous supply of air from the windbox to all portions of the grate, which in addition to supplying the proper amounts of air to the fuel for combustion, also results in main- It should be noted that because the obliquity or angle of inclination of the slots with respect to the direction of grate movement in one group of slots is opposite to that in an adjacent group of slots the travelling grate does not tend to creep toward one side or the other of the stoker as would be the case if all of the slots extended obliquely toward one side of the plates and stoker.

It should also be noted'because the recesses on opposite edges of each plate are offset, the

plates I6 may be installed alongside each other in a stoker without the necessity of noting which side should be placed against a plate already in place.

The grate links l3 are interconnected by rods 32 extending through transverse apertures near each end of a link. However, the plates l6 as described herein may also be employed in stokers wherein the grate "keys are mounted on bars extending transversely of the stoker.

As mentioned, the grate links l3 are formed with transverse apertures near each end. With the links in staggered relation apertures at opposite ends of adjacent links are alined so that rods 32 may be passed therethrough to interconnect the links, a transverse row made up of laterally alined links being-mounted on a pair of rods each of which also connects With one end of links in the preceding or following transverse row. In addition to interconnecting links to form a continuous surface the rods 32 also serve to connect the links [3 to chains of driving links which are located at points spaced transversely of the grate. There is a driving chain at or near each edge and, if desired, other chains may be provided at intermediate points also.

What I claim is:

1. In a furnace, the combination with a travelling grate formed of a series of grate links arranged to provide air spaces therebetween, and an air ch'amber beneath the grate; means forming a top closure for said chamber and constituting a surface on which said grate links ride comprising a series of plates each formed with a plurality of air slots extending at an oblique angle with respect to the direction of movement of the grate.

2. In a furnace, the combination with a travelling grate formed of a series of grate links arranged to provide air spaces therebetween, and an air chamber beneath the grate; means forming a top closure for said chamber and constituting a surface on which said grate links ride comprising a series of plates arranged in side by side relation and each having the side edges thereof that extend in the direction of grate movement formed with a plurality of recesses spaced longitudinally of the plates, the recesses on one edge of each plate being staggered with respect to the recesses on its opposite edge.

3. In a furnace, the combination with a travelling grate formed of a series of grate links arranged to provide air spaces therebetween, and

an air chamber beneath the grate; means forming a top closure for said chamber and constituting a surface on which said grate links ride comprising a series of plates arranged in side by side relation and each having the side edges thereof that extend in the direction of grate movement formed with a plurality of recesses spaced longitudinally of the plate, the recesses on one edge of each plate being staggered with respect to the recesses on its opposite edge so that non-recessed portions on the side edge of one plate lie opposite recesses on the adjacent side edge of an adjacent plate; and means laterally spacing adjacent plates to provide spaces between their side edges intermediate their ends for placing the recesses at the edge of one plate in communication with those at the edge of the other plate lateral to form a continuous zig-zag slot.

4. A supporting surface for a travelling grate as recited in claim 1 characterized in that groups of slots formed in said plates are inclined in one direction and spaced in the direction of grate movement from groups of slots that are inclined in the opposite direction.

5. A supporting surface for a travelling grate I as recited in claim 1 characterized in that groups of slots formed in said plates are inclined in one direction with respect to the direction of grate movement and are spaced transversely of the grate from groups of slots that are inclined in the opposite direction.

6. A supporting surface for a travelling grate as recited in claim 1 characterized in that said slots converge from opposite side edges of each plate toward the middle thereof.

, '7. A supporting surface for a travelling grate as recited in claim 2 characterized in that said 

